Various microphones that can be connected to an external device, for example, to a mobile telephone or to a computer are known. Such a microphone may be part of a headset, for example. Often, further peripheral devices besides the microphone need to be connected to the external device. If a headset with a microphone is connected to a mobile telephone, for example, it is also possible to connect an input device, which allows the volume to be adjusted, for example, to the central device. Peripheral devices can furthermore be connected to a central device together with a microphone for a wide variety of further functions. Examples in this regard are further microphones for noise reduction or cameras for video recording.
If a further peripheral device, for example, an input device, is connected to a headset with a microphone which is connected to an external device, there is then the problem of transmitting data from this peripheral input device to the central device.
A solution to this problem is disclosed in WO 2009/091660 A1. This document describes a headset with an input device which can be connected to a mobile telephone or a computer by means of a jack plug. Data transmission from the input device to the computer or the mobile telephone involves the use of the same signal channel as is also used for the data transmission from the microphone in the headset. To this end, the signals produced by the input device are converted into ultrasonic signals. These ultrasonic signals do not disturb the signals on the microphone, since they are imperceptible to human hearing. The solution to the aforementioned problem as disclosed in this document is very specific, however, and is suitable only for instances in which the signals from the peripheral device can be meaningfully converted into ultrasonic signals.
WO 2009/091660 A1 proposes using the signal channel of the microphone for the data transmission between the peripheral device and the central device. Various drawbacks arise in this context, however. Firstly, this requires the peripheral device to be equipped with complex switching logic, and secondly the signal channel of the microphone can be used to transmit only a limited number of signals. Particularly if the peripheral device is a mechanical device which does not have any semiconductor circuits, the implementation of an interface in the peripheral device is very complex.
A further solution to this problem is disclosed in the German publication DE 102005042904 B4. In this case, a microphone capsule is connected to a controller by means of a preamplifier and an analog-to-digital converter. The controller is in turn connected to an external device, e.g., a computer or a mobile telephone, by means of an interface. The controller is also connected to an input device which has a display and buttons. The input device communicates with the external device via the controller and the interface.